[U-Boot-Users] struct NS16550 {...} __attribute__ ((packed)) at ns16550.h

[Wolfgang Denk]

In message <OF34DF8405.50E611E8-ON85256FEB.0051A68A-85256FEB.00522DF9 at smsc.com> you wrote:
> 
> We are using u-boot for proprietary ARM board with NS16550 compatible serial controller.
> It is configured as 4bytes access to serial controller, so set CFG_NS16550_REG_SIZE to 4.
> But, because of "__attribute__ ((packed))" of struct NS16550, all register accesses to NS16550 are generated to byte
> access (LDRB, STRB in ARM).

No, this staement makes no sense to me.

> I think it should NOT have __attribute__ ((packed)) if NS16550 is configured as 4bytes access.
> Am I missed something?

I think so.

"__attribute__ ((packed))" only affects the alignment of the  entries
in the structure. It has no influence on how to access these entries.
If  your  access is a 32 bit read or write access then it will not be
changed whether there is a "__attribute__  ((packed))"  in  place  or
not.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Every program has at least one bug and can be shortened by  at  least
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every program can be reduced to one instruction which doesn't work.